Three dimensional (3D) time-of-flight (TOF) cameras are active-type systems. In general, systems are based on the homodyne phase-measurement technique of emitted intensity-modulated light, which is reflected by the scene. The reflected light is imaged onto a sensor. The photo-generated electrons are demodulated in the sensor synchronously with the emitted-modulated light, and based on the phase information, the distance between the camera and the scene for each pixel is deduced.
A major problem of a TOF system is that the sensor has to handle high dynamic ranges. The modulated signal received by the camera drops with the square of the distance. Furthermore, the reflectivity of the targets might vary to a large degree. Both of these factors contribute to the high dynamic range.
As an example, the image might contain a bright object at 30 centimeters (cm) with a reflectivity of 100% and a dark object at 300 cm with a reflectivity of 10%. Therefore, the dynamic range to cover becomes:
  DR  =                              300          2                *        100                              30          2                *        10              =                  1        ′            ⁢      000      
The challenge of the high dynamic range in TOF imaging has been described by B. Buettgen in “CCD/CMOS lock-in pixel for range imaging: Challenges, limitations and State-of-the-art”, Proceedings of the 1st Range Imaging Research Day at ETH Zurich, 2005.
Due to this high dynamic range requirement, stray light originating from the strong signal adding to the weak signal is a dominant problem for numerous applications of the TOF technology. A solution has been proposed by James Mure-Dubois et al. in “Real-time scattering compensation for time-of-flight camera”, Proceedings of the 5th International Conference on Computer Vision Systems (ICVS 2007). A similar approach has been presented by T. Kavli et al. in “Modelling and Compensating Measurement Errors Caused by Scattering in Time-Of-Flight Cameras”, Proceedings of SPIE, Vol. 7066, 2008.
However, in both aforementioned approaches the required computing power required makes it less feasible to embed the solution in high speed acquisition applications.